British diplomats lobbied Pope John Paul II repeatedly to secure his assistance in ending the IRA's 1980 hunger strike, exchanges between Margaret Thatcher and the Vatican reveal.

Documents available at the National Archives from today also demonstrate how, as part of the propaganda war against the republican protest, UK embassies were instructed to discover whether prisoners around the world had to wear uniforms. Even the releaxed dress code of Liechtenstein's inmates was recorded.

The Provisional IRA and Irish National Liberation Army (INLA) members had launched a hunger strike in the Maze prison with five demands for their political status to be recognised, including the right not to wear a uniform or do prison work.

In the run-up to the confrontation, the Foreign Office asked diplomats to report on the use of uniforms in other countries. "The practice of wearing prison uniforms in Spanish goals was discontinued," a diplomat in Madrid wrote.

In Italy, prisoners dressed in "khaki-coloured suits". In Austria, convicts had uniforms "of quite good quality and by no means blatantly distinctive". In Portugal, the suits, it was said, "would not attract attention since [they were] the sort worn by the average labourer".

Swiss criminals, the embassy in Berne noted, were not required to wear uniforms and "the foregoing also applies to Liechtenstein". Convicted prisoners in Turkey were not obliged to wear prison uniforms, a diplomat in Ankara added, "if only because the government does not provide any".

Humphrey Atkins, the Northern Ireland secretary, cannot have been reassured. Secret cabinet minutes on 23 October record him proposing to issue a statement making clear "that the government [was] in no circumstances prepared to grant special status to the PIRA prisoners but that as part of the continuing process of penal reform they were prepared to allow all prisoners to wear approved civilian clothing.

"[Atkins] considered that a statement on those lines would deprive the protesters of a great deal of public sympathy … and would be better made now than at a later stage when it could be presented as a surrender to the prisoners' action."

The prime minister agreed but insisted that "once the government's position had been made clear, no further concessions should be offered." Similar comments – such as "We cannot make any concessions" – appear in the margins of other cabinet documents on the hunger strike in Thatcher's charcteristic blue felt pen.

The government's slight shift in position did not deter the hunger strikers. Seven republican volunteers in the H-Blocks refused food on 27 October 1980. A report sent to the cabinet in early November warned that republican families "are very willing for their kin to die for the cause".

There was also disappointment in the cabinet that while "individual priests (such as Fr Faul) are undoubtedly doing their best, the church is not being particularly helpful. Cardinal O'Fiaich and Bishop Daly have not as yet taken a very constructive line."

But there were plans to stiffen the resolve of the Catholic church. Sir Mark Heath, the British ambassador to the Vatican, had been summoned to convey a personal message from the pope to the prime minister.

"I would ask you to consider personally possible solution in order to avoid irreversible consequences that could perhaps prove irreparable," the pope's letter to Thatcher pleaded.

The ambassador added a covering note: "When I asked what further practical steps he thought we could take in addition to the concession on clothing, he was silent. [The pope] said that the clergy would continue to urge the prisoners to give up their strike and [that] the message was a personal one from the pope himself."

On 24 November the prime minister flew to Rome and met John Paul II. On her return she penned a grateful letter. "I derive encouragement, instructions and inspiration from our discussion," she told him. "Your wisdom and experience are of inestimable value to us all. I will continue to reflect for a long time on what you said."

She continued: "I and my colleagues in the government are firmly resolved that it would be utterly wrong … to take any steps which could be regarded as conceding that political motives can excuse murder or serious crimes.

"In view of the sensitivy of the issue involved, I have asked HM minister to the Holy See to seek an early opportuinity to explain matters more fully to the cardinal secretary of state; and for that purpose I am arranging for a senior official … in the Northern ireland Office to go to Rome to assist Sir Mark Heath."

The prime minister also told the pope: "You may be sure we very much welcome the efforts of the clergy in Northern Ireland to persuade the prisoners both to give up the strike and to end their protest; and I hope you will be able to give full support to this objective."

In mid-December, after a plea from Cardinal O'Fiaich as one of the hunger strikers approached death, the protest was called off. The recriminations soon began; a second – and more deadly – hunger strike was launched the following year.